The present invention relates to a torque transmission apparatus for transmitting torque from a driving source to a rotating device, and in particular to a torque transmission apparatus (pulley) that transmits torque from an engine to rotating devices (auxiliary machines), such as an alternator or a compressor in a vehicle engine compartment.
The applicant filed a patent application for a pulley (Japanese Patent Application No. 2001-120161) with a built-in rubber damper for absorbing torque fluctuations. However, when the torque fluctuations are to be absorbed by only the rubber damper, the pulley must to be larger, because a larger damper is required for larger torque fluctuations.
The present invention was made in view of the above-mentioned problem, and it is an object of the invention to absorb torque fluctuations (vibration), while limiting the outside dimensions of the torque transmission apparatus.
To achieve the above-mentioned object, according to a first aspect of the present invention, a torque transmission apparatus for transmitting torque from a driving source to a rotating device includes a first rotating member, which has a dual tubular form. The first rotating member includes an inner tube and an outer tube, which are coaxial. The outer tube receives torque from one of the driving source and the rotating device. A bearing is located inside the inner tube, for supporting the first rotating member. A second rotating member is connected to the other of the rotating device and the driving source. An elastically deformable torque transmission member is located between the inner tube and the outer tube, for transmitting the torque between the first rotating member and the second rotating member. A pendulum type vibration-absorbing mechanism is located between the inner tube and the outer tube for canceling an exciting force generated corresponding to a rotational movement of both of the rotating members. The mechanism includes a movable weight.
With this apparatus, it is possible to absorb torque fluctuations (exciting force, vibration) sufficiently, while reducing the outside dimension of the torque transmission apparatus, in comparison to an apparatus in which the torque fluctuations (exciting force, vibration) are absorbed only by an elastically deformable torque transmission member.
It is preferred that the vibration-absorbing mechanism be constituted by fitting the weight into a hole formed between the inner tube and the outer tube. The center of gravity of the weight is offset from the center of area of a section of the hole.
An annular portion, which is provided with an engaging member for engaging the torque transmission member, is formed on the second rotating member, and the hole is blocked by the annular portion. Thus, escape of the weight portion from the hole is prevented.
In addition, escape-preventing means for preventing the weight portion from falling out of the hole may be provided on the torque transmission member adjacent to the hole.
The cross sectional shape of the space occupied by the weight is roughly the same as a shape that is a combination of the hole shape of a first opening and the hole shape of a second opening. The first opening is an opening of the hole at one end of the hole, and the second opening is an opposite opening.
With this arrangement, it is possible to easily form escape-preventing means, such as a wall portion for preventing the weight portion from falling out of the hole, integrally at both ends in the axial direction of the hole.
A sheathing film made of resin may be provided on an outer wall of the weight portion that faces an inner wall of the hole.
This reduces noise created when the weight portion collides with the inner wall of the hole.